The principle of controling insulin gene expression in somatic cell gene therapy was studied in three ways. The first method used fibroblasts which secrete human proinsulin by recombinant technology. these fibroglasts were transfected with the second recombinant plasmid encoding mouse genomic CD8.2 gene. These doubly transfected cells were trans-planted intraperitoneally to streptozocin-induced diabetic C3H mice. The blood glucose concentrations were remarkably decreased from 430 mg/dl of the pre-treatment level to 80 mg/dl at the 30th day after the transplantation. To remove the transplanted cells, anti-CD8.2 monoclonal antibody was administered, which lead to the reversal of blood glucose level to the pre-treatment level, proving the complete removal of transplanted cells. The second method used MIN-6 cells which originated from transgenic mice with a Rat-Insulin-Promoter-T-antigen transgene. The transplantation of this cell line to diabetic C57BL06 mice immediately improved blood glucose levels to the normal range. Along with the time after transplantation, glucose responsiveness of transplanted cells decreased as estimated by glucose tolerance test. Thirdly glucose-dependent mechanism of insulin secretion in this B-cell line was examined by culturing this cell line in different glucose concentrations, which showed minimul change of insulin mRNA in contrast to 6-fold difference of insulin secretion. This suggests the importance of translational control rather than transcriptional control. The future study on the glucose-dependent regulation of insulin secretion should be directed to the molecular analysis of glucose-dependency in this MIN-6 cell line. It is also important to use B-cell-derived cell lines as well as fibroblasts as the possible target of somatic cell gene therapy against diabetes.